Fiber products and methods of manufacturing comprising base sheet of cellulose fibers saturated with a mixture comprising elastomeric polymer and polar adjunct polymer having carboxylic acid functional group



March 1952 J. F. HECHTMAN ET AL 3,025,217

FIBER PRODUCTS AND METHODS OF MANUFACTURING COMPRISING BASE SHEET OF CELLULOSE FIBERS SATURATED WITH A MIXTURE COMPRISING ELASTOMERIC POLYMER AND POLAR ADJUNCT POLYMER HAVING CARBOXYLIC ACID FUNCTIONAL GROUP Filed April 11, 1958 4 29/455 55 557 0F (ELM/L055 F/BER5 6/7 rumqnso WITH f7 MIXTURE c0MPH/5/A 6:

(l) ELHSTOMER/C POL YME/F; HNO

(2) POL/IR flUJl/NCT POLYMER HA V/NG C/IRBOX YL/C c/a FUNCTION/IL GROUP United States Patent M 3,026,217 FIBER PRODUCTS AND METHODS OF MANUFAC- TURING COMPRISING BASE SHEET OF CELLU- LOSE FIBERS SATURATED WITH A MIXTURE COMPRISING ELASTOMERIC POLYMER AND POLAR ADJUNCT POLYMER HAVING CAR- BOXYLIC ACID FUNCTIONAL GROUP John F. Hechtman and Edwin G. Greenman, Munlsmg, Mich., assignors to Kimberly-Clark Corp., Neenah, Wis., a corporation of Delaware Filed Apr. 11, 1958, Ser. No. 727,797 6 Claims. (Cl. 117-155) This invention relates to saturated fibers, and more particularly to fiber sheets impregnated with compositions having specific adherence thereto. This application is a continuation-in-part of application Serial No. 675,017, filed July 30, 1957.

In the past, various elastomers, including natural and synthetic rubbers, have been the principal commercial saturants for paper impregnation. Elastomer saturants possess the desired physical properties in some degree necessary for paper impregnation. However, even though the elastomers, by themselves, possess desirable tensile and stretch properties, their adhesion to cellulose is poor. The result is that the desirable properties of the elastomer films are not fully imparted to the finished impregnated sheet.

High adhesion of a saturant to the fiber is an important requirement in order to obtain adequate tensile strength and maintain continuity of strain under stress. Adhesion may be obtained by chemical reaction, physical attraction, or mechanical entanglement. Mechanical entanglement alone is inadequate to produce sulficient adhesion and must be supplemented by the other forces. While physical attraction may be adequate when a sheet is dry, it may be destroyed when a sheet is wet. hesion by a chemical bond between the saturant and the cellulose, which is not affected by Water or other liquids, is highly desirable.

The desirable physical characteristics of a saturated fiber sheet for some uses may be summarized by a property known as toughness. Although toughness is a complex characteristic, it may be generally defined by the stress-strain properites of a sheet. Toughness attains its highest level by a correct combination of tensile strength and stretch. Among the other desirable characteristics of a saturated sheet are high wet strength propcellulose.

3,026,217 Patented Mar. 20, 1962 2 erties, high folding endurance, high flexibility, high in ternal tear, high edge tear, high delamination resistance, and resistance to physical degradation and discoloration due to heat and light aging.

It is, therefore, an object of the invention to provide impregnated sheets which have an enhanced high degree of toughness. It is a further object of the invention to provide a sheet of saturated fibers with an improved high degree of stretch and of desirable dry and wet tensile strength. It is another object of the invention to provide impregnated cellulose sheets having a high degree of flexibility. It is yet another object of the invention to provide the sheets with good fold endurance. It is still another object of the invention to provide a saturated sheet with a high delamination resistance. It is a further object of the invention to provide a saturated sheet with high, internal and edge tear. It is still a further object of the invention to provide a saturated sheet with resistance to physical degradation and discoloration due to heat and light aging. It is another object of the invention to provide a saturant composition that is inexpensive. Further objects of the invention will be apparent from examination of the ensuing description and appendant claims.

Briefly stated, the present invention relates to a paper product comprising a sheet of cellulose fibers impregnated with a composition comprising an elastomer and a compatible adjunct polymer with specific adhesion to More particularly, the adjunct polymer has polar functionalgroups which tend to adhere to cellulose.

The accompanying drawing illustrates in cross-section a product prepared in accordance with the invention in which a base sheet of cellulose fibers is saturated with a mixture comprising an elastomeric polymer and a polar adjunct polymer.

In accordance with the objects of the invention it has been discovered that an adjunct polymer with specific adherence to cellulose imparts its adhesive properties to the elastomer which, by itself, has a low level of adhesion. By this discovery the desirable functional properties of elastomers are imparted to the saturated sheet.

BASE SHEET The base sheet is an open porous fiber web. The sheet may vary from low to high bonded fibers. Tables I and H below illustrate some of the major properties of typical cellulose base sheets.

Table I PHYSICAL PROPERTIES AND FIBER IDENTIFICATION OF UNSA'IURATED CELLULOSE BASE SHEETS RANGING FROM LOW BONDED TO HIGH BONDED PAPERS Exnrnnln l 2 3 4 5 6 7 8 9 10 Basis weight 23.8 23. 9 33. 6 38. 5 25. 6 32. 0 14. 0 14. 2 14. 0 15, 5 Caliper 21. 6 21. 8 21.0 16. 3 9. 97 10. 3 4. 7 5.07 4. 40 5.05 Apparent densityl. 10 l. 09 l. 2. 36 2. 57 3. 10 2. 98 2. 8D 3. 18 3. 10 Tensile sum/lb 0. 078 0. 066 0. 08 O. 120 0. 164 320 320 370 0. 450 0. 67 l. 91 1. 2. 1 l. 2.26 2. 2 2. 20 2. 20 2. 2

0. 25 16 O. 8 2.1 8. 5 l7. 4 6. 0 7. 9 27 97 114 36 12. 0 Number of presses used in mfg None None None 2 1 1 2 R lativ degrge f reflm'ng Slight Slight Slight Hard Med Hard Med. Med Hard V. hard 3 Table II LABORATORY BEATER EVALUATION OF VARIOUS PULPS AND IDENTIFICATION OF PULPS NOT COV- ERED IN TABLE I Beating Porosity Time Ex. time, Basis Appar. Tensile Tear of mm. weight dens. sum/lb. climb,

Gurley Frazier see.

1 Hour.

Fiber identification of pulps used in each of the examples listed in Tables I and II are as follows:

Example 9Kraft pulped Norwegian pine. Bleached. Example l0-Kraft pulped spruce fiber. Bleached. Example 11-Same as Example 2.

Example 12Same as Examples 3 and 4.

Example 13-Sarne as Example 5. Example 14Sulfite pulped spruce fiber. Conventional alpha treatment. Bleached.

Example 15Same as Example 9.

Example l6--Same as Example 10.

Example 17Sulfite pulped spruce, balsam and poplar mixture. Hypochlorite bleached.

Example 18-Kraft pulped hard wood mixture. Conventional alpha treated. Bleached.

The units used in the above Tables I and II and also in the specification and claims are defined as follows.

Basis weight: Weight in pounds of a ream of paper 17 inches x 2 inches per 500 sheets, weighed at 50 percent Essentially the same as All subsequent tests are made on like conditioned paper.

Caliper: Thickness of a single sheet 'of paper expressed in mils or thousandths of an inch, as by TAPPI Method T411-m-44.

Apparent density: Apparent density is determined by dividing the basis weight by the caliper to yield the ream weight in pounds per mil of thickness.

Dry tensile strengthMachine and cross direction: The breaking strength as determined on a pendulum type tester having a bottom jaw travel of 12 inches per minute. The test is performed on a strip 15 mm. wide, and the tensile strength is reported in kg./15 mm. strip width. TAPPI Method T404-m-50.

Tensile sum per pounds of basis weight: This index is obtained by dividing the sum of the machine and cross direction tensiles in kg./15 mm. by the basis weight.

Tensile ratio: A dimensionless number which is obtained by dividing the machine direction tensile by the cross machine tensile and is primarily used as a restriction in comparing tensile sums of paper having large differences in tensile ratios. Most Fourdrinier saturating papers in the weight range of 10 lbs. up have ratios of 1.4 to 3.5. Cylinder machine grades may have ratios of as high as 10. V v

Porosity: Gurley porosity is'ofonly limited value in evaluating low bonded papers since the porosity is below the useful range of the instrument. 0n low bonded papers Gurley porosities have been found of 0.3 second per cc. for eight sheets having a basis weight of 35 lbs. A Frazier porosity tester has been found better suited for determining the porosity of low bonded papers. The units of Frazier porosity are cubic feet of air flow through the material per minute per square foot under a difierential head of 0.5 inch of water.

Time of climb: Time in seconds for distilled water to climb 1.0 inch above the water level when the end of a vertically suspended machine direction strip 1.0 inch wide is immersed in the distilled water.

Tear: Internal tearing resistance of paper as described by TAPPI Method T414-m-49.

Although the base sheets are usually formed entirely of cellulose fibers, sheets containing both cellulose and synthetic fibers, or exclusively synthetic fibers, are also satisfactory. These base sheets may be formed on a conventional paper machine, or by other methods.

SATURANT COMPOSITIONS The paper product of the invention is impregnated with a composition containing an elastomer having in admixture therewith a compatible adjunct polymer with specific adhesion to cellulose. The impregnation is preferably made from aqueous dispersions of the elastomer and adjunct polymer, but may also be made from other systems such as organic solutions of the elastomer and adjunct polymer.

Elast0mers.The elastomers usable in the compositions include synthetic rubbers, for example copolymers of acrylonitrile and butadiene; copolymers of butadiene and styrene; polybutadiene; polychloroprene; copolymers of isobutene and isoprene; terpolymers of butadiene, acrylonitrile, and styrene; terpolymers of ethyl acrylate, acrylonitrile, and butadiene; and the like which are polymers and copolymers of conjugated dienes; and natural rubber.

These polymers have been well known impregnants in the past for cellulose fibers, and have constituted the principal commercial saturants to the present time. They are widely reported and discussed in the literature, and in prior patents.

Adjunct p0lymers.-The adjunct polymers have a specific adherence to cellulose. They should be reasonably compatible with the elastomer and possess reasonably similar stress-strain properties.

The adjunct polymer has polar substituent groups with a specific adherence to cellulose, for example carboxylate groups. The adjunct polymer can be a copolymer formed from at least one polymerizable, unsaturated carboxylic acid in which the unsaturation is a double bond, or ethylenic linkage, and at least one alkyl acrylate in which the alkyl group has from one to four carbon atoms. Examples of polymerizable mono-unsaturated a,B-ethylenic carboxylic acids include: acrylic acid, methacrylic acid, itaconic acid, aconitic acid, maleic acid, fumaric acid, and the like. Examples of alkyl acrylates include the esters of primary alkanols, such as methyl acrylate, ethyl acrylate, propyl acrylate and butyl acrylate; and esters of secondary alkanols, such as iso-propyl acrylate, iso-butyl acrylate. These copolymers are of a softness such that hardening comonomers may be introduced. Examples of such hardening comonomers, include the alkyl methacrylates in which the alkyl group may have from one to four carbon atoms, for example, the methyl, ethyl, propyl, iso-propyl, butyl, and iso-butyl methacrylates.

The proportions of the monomers used to produce the copolymer, for example, may be from about 0.5 to about 7% by weight of a carboxylic acid compound, at least 80% by weight of an alkyl acrylate, and from to 19.5% of an alkyl methacrylate.

The following list gives several typical copolymer systems, in which the percentages are by weight:

Ethyl acrylate 84.5%, methyl methacrylate 10.5%,

itaconic acid, 5.0%

Ethyl acrylate 85%, methyl methacrylate 10%, acrylic acid 5.0%

Ethyl acrylate 95%, acrylic acid Ethyl acrylate 95%, methacrylic acid 5% Techniques for polymerizing the foregoing monomers into the copolymer are further illustrated in Patents Nos. 2,795,564, 2,760,886, 2,790,736 and 2,790,735.

The copolymer dispersions may be made by any of the known emulsion copolymerization procedures, e.g. by first mixing the several monomers in the desired proportions into an aqueous solution of an anionic, or preferably a non-ionic, dispersing or emulsifying agent.

Examples of anionic emulsifying agents that may be used include the higher fatty alcohol sulfates, such as sodium lauryl sulfate, the alkylaryl sulfonates, such as sodium t-octylphenyl sulfonates, the sodium di-octyl sulfosuccinates and so on. Examples of the non-ionic dispersing agents that may be used for preparing the monomeric emulsions before copolymerization or dispersions of the polymer after polymerization include the following: alkylphenoxypolyethoxyethanols having alkyl groups of about seven to eighteen carbon atoms and 6 to 60 or more oxyethylene units, such as heptylphenoxypolyethoxyethanols, octylphenoxypolyethoxyethanols, methyloctylphenoxypolyethoxyethanols, nonylphenoxypolyethoxyethanols, dodecylphenoxypolyethoxyethanols, and the like; polyethoxyethanol derivatives of methylene like alkyl phenols; sulfur-containing agents such as those made by condensing 6 to 60 or more moles of ethylene oxide with nonyl, dodecyl, tetradecyl, t-dodecyl, and the like mercaptans or with alkylthiophenols having alkyl groups of 6 to 15 carbon atoms; ethylene oxide derivatives of longchanged carboxylic acids, such as lauric, my-ristic, palmitic, oleic, and the like, or mixtures of acids such as found in tall oil containing 6 to 60 oxyethylene units, etc.; block copolymers of ethylene oxide and propylene oxide com- Other reducing agents include water-soluble thiosulfates' and hydrosulfites. Activators or promoters in the form of the salts (such as the sulfates or chlorides) of metals which are capable of existing in more than one valence state such as cobalt, iron, nickel, and copper may be used in small amounts. The most convenient method of preparing the copolymer dispersions comprises agitating an aqueous suspension of a mixture of copolymerizable monomers and a redox catalytic combination at room temperature without the application of external heat. The amount of catalyst can vary but for purposes of efi'iciency from 0.01% to 1.0%, based on the weight of the monomers, of the peroxidic agent and the same or lower proportions of the reducing agent are recommended. In this way it is possible to prepare dispersions which contain as little as 1% and as much as 60% or 70% of the resinous copolymer on a weight basis. It is, however, more practical (hence preferred) to produce dispersions which contain about 30% to 50% resin-solids.

In order to obtain wet state, or latex, compatability of the elastomer with the adjunct polymer it might be necessary to replace the anionic emulsifier of the elastomer with a non-ionic emulsifier, so as to prevent coagulation of the anionic elastomer by the polar functional groups, such as carboxylate radicals, of the adjunct polymer. Also, in some instances, it is necessary to adjust the pH of the latex composition, for example, Within the range of from 5.0 to 7.5, to maintain a suitable saturant composition viscosity and maintain an adequate degree of penetration of the latex composition into the base sheet.

Salts of heavy metals such as calcium, zinc, barium, and magnesium oxides may be used to improve the solvent resistance, improve the heat and light stability, improve dry tensile strength, and increase the rate of wet strength development on heat aging. Dispersions of zinc oxide have been found particularly suitable in the range of 0.05 to 4.0 parts per parts of the polar adjunct copolymer on a dry solids basis.

Conventional rubber antioxidants may be employed in the composition to enhance the heat and light stabiilty.

SATURATION TECHNIQUES Saturation of a dry sheet may be accomplished in the following manner. Roll stock of unsaturated base paper is fed into the saturating head. The saturating head may be a float tank prior to the squeeze rolls in which the paper is floated on the surface of an aqueous dispersion, or latex, of the saturant composition and becomes im pregnated by capillary forces carrying the saturant into the sheet. Another type of saturating head is a shower pipe at the squeeze roll. The sheet is passed into the squeeze roll nip at a downward angle and the saturant latex is supplied by means of a shower pipe to the trough formed by the paper and top squeeze roll. Excess latex is removed by squeeze rolls, water is evaporated by passing the sheet over heated can driers, and the dried sheet is wound up in a roll. As alternate drying methods, a festoon or tunnel driers may be used.

7 The ratio of dry saturant composition to fiber for a given base sheet is controlled primarily by the dry solids of the saturant. A secondary but minor control is effected by the nip pressure on the squeeze rolls.

The latex may contain solids in the range of about 0.1 to about 65 percent depending upon the saturant to fiber sity and void volume of the base sheet. Low fiber to fiber 15 bonded sheets, by virtue of their low apparent density, offer the opportunity of obtaining high ratios of saturant to fiber. For example, a medium bonded sheet using a saturant composition in parts per hundred parts of dry fiber.

Table Ill-Part I SATURANT FORMULATIONS MAJOR COMPONENTS AND SATURANT PICKUPS PARTS DRY SATURANT PER 100 DRY FIBER ON MEDIUM HIGH BONDED FLAT- BACK TAPE STOCK ratio desired in the saturated product, although the usual I range is from about 20 to 50 percent. A majority of Example A B products are made within the range from about 35 to about 160 parts of dry saturant per 100 parts by weight 10 g'i gi fifiga 8 2g of fiber, although it is possible to produce useful prod- A nti0l{i(lant 1 1.5 1 5 nets in the range of 0.1 to 200 parts dry saturant per 100 ggt ggfi g gifif 1; if I parts by Weight of fiber, depending on the apparent denppp p 76 76 75 and a carboxylic acid compound 0 Table IIl-Part II PHYSICAL PROPERTIES OF SATURATED SHEETS-HEAT TREATED (HT) AND UN- TREATED (U)FROM SATURANTS IN TABLE I A B C U HT HT U lElI'I HT U HT H'I Basis Weight 22. 2 22. 1 22.1 22.3 22. 3 22.1 22. 2 22. 3 22. 2 Apparent density 5. 29 5.02 5.10 5. 27 5.11 5. 5. 29 5.14 5. 26 Dry tensile:

C 2.4 2.6 2.6 2.7 2.7 2.7 3.0 3.0 3-0 Dry stretch:

CD 17. 9 16. 5 16. 1 25. 6 21. 0 21. 7 26- 6 21. 8 21- 2 \Vet tensile, MD"- 0.20 0.45 0. 64 0.34 1. 90 2. 21 0. 41 2. 32 2. 57 Wet stretch, MD 0.0 6.2 6.8 4. 7 12. 3 14.3 5. 4 12.4 13.0 Fold, MD 248 223 233 243 255 224 304 346 385 Delamination resistance, M 642 648 719 752 877 829 886 976 976 Reflectance-R 458 A- 78. 0 69. 0 66. 1 79. 2 74. 1 71. 1 79. 1 73. S 71. 5

1 Heat treated 3 hrs. at 105 C.

1 Heat treated 6 hrs. at 105 C.

saturant wlth 50% dry solids can obtain a pickup of 100 45 Table [IL-Part 111 parts of saturant as dry solids, while low bonded sheets pick up 200 parts of saturant as dry solids per 100 parts by weight of dry fiber.

PHYSICAL PROPERTIES OF UNSATURATED BASE SHEET-FLATBACK TAPE STOCKMEDI'UM HIGH BONDED In general, pickups in the range of 35 to 75 parts appear to be optimum, both from the standpoint of eco- Basic Weighl 12.5 nomics and physical property performance. On the other gis gz g g i hand, pickups are set at the level required for the sheet Tensile h to perform properly in its end use. For example, when Time f high delamination, abrasion, and scuff resistance are re- Porosity, Gurley 42.0

quired, the pickup level may be set at 75 to 160 parts per Example D E TableIV-Jart 1 60 SATURANT FORMULATIONS-MAJOR OOMPONENTS- AND SATURANT PICKUPS-PARTS DRY SATURANT PER 100 PARTS DRY FIBER-ON MEDIUM BONDED FLAT- BAOK TAPE STOCK reduce the temperature. Heat treatments of 0.5 -to 20 Polar adlun tz 0 15 3o 45 60 100 n o Antioxidaut. 1 5 1.5 1.5 1 5 1.5 1 5 1 5 hours at temperatures above 100 C. may be employed, Ptarcenttotal solids" 45 45 45 45 45 45 45 although about 1 to about 7 hours at about 105 C. are P10kl1pppl1p 97 9a 95 9s 95 39 93 most generally used. Naturally, practical equivalent time-temperature relationships may be used.

The following examples are given to further illustrate the invention. All percentages and parts are by weight.

O0p0lymer of acrylonitrile (31.5%) with butadiene (68.5%). Total S0l1dS-54%. Particle s1ze1,500 A. Emulsifier system-anionic. Mooney viscosity65 (ML-4 2 Acrylate copolymer of ethyl acrylate (95%) and a carboxylic acid Pickup is listed as pphp Which refers to the pickup of P (5%).

Table IVPart II :EHT) AND UNTREATED (U)FROM SATURANTS IN D E F G H I J U HT U HT U HT U HT U HT U HT U HT 215 8 Weight 23. 8 23. 5 23. 7 23. 3 24. 6 23. 8 25. l 24. 9 24. 7 24. 2 24. O 24. 24. 23. 8 %pp dens1ty 4. 69 4. 67 4. 81 4. 93 4. 78 4. 76 4. 85 5. 00 5. 5. 01 4. 85 4. 85 4. 92 4. 98

7. 8 10. 4 16. 4 13. 4 12. 1 12. 9 14. 3 15. 8 15.1 13. 0 11. 5 13. 8 13. 0 ll. 4 7 CD 16. 8 22. 5 26. 8 23. 4 25. 9 27. 5 28. 5 26. 4 30. 3 26. 6 23. 1 24. 0 24. 3 27. 0 E et tensile, MID. 0. 1. 07 0. 58 2. 66 0. 69 3. 28 0. 85 3. 50 O. 60 3. 52 0. 62 3. 79 0. 61 3. 51 E ia Stretch, MD 8. 3 6. 0 4. 0 14. 8 4. 9 16. 8 5. 1 15. 4 4. 3 16. 5 5. 1 12. 4 5. 4 15. 8

MD 201 363 215 377 191 341 299 526 628 872 684 1, 163 788 1, 172 D 46 91 60 90 49 63 68 110 114 174 117 272 252 274 Delarn. resist, MD" 575 819 696 762 865 925 1, 050 l, 120 1, 148 l, 171 1, 021 1, 214 947 l, 259

1 Heat treated 5 hrs. at 105 C.

Table lVPart III PHYSICAL PROPERTIES OF UNSATURATED BASE SHEETFLATBACK TAPE STOCK BASEMEDIUH BONDED Basis weigh Caliper Apparent density Tensile sum/ Ratio Gurley porosity Time of climb Table VPart I SATURANT FORMIULATIONS-MAJOR COMPONENTS- AND SATURANT PICKUPPARTS DRY SATURANT PER 100 PARTS DRY FIBER-ON MEDIULI BONDED CREPED TAPE STOCK Mooney viscosity65 (ML4).

2 Acrylate copolymer of ethyl acrylate (95%) and a earboxylic acid compound (5%).

Table VPart II PHYSICAL PROPERTIES OF SATURATED SHEETS-HEAT TREATED (HT) AND UNTREATED (U)FROM SATU- RANTS IN TABLE III-PART I U HT 1 U HT 1 Basis weight 23. 6 23. 2 23.8 23. 9

Apparent density 3. 55 3. 49 3. 56 3. 66 Tensile:

CD 2. 5 2. 6 2. 5 2.6 Stretch.

Delamination resistance, MD 839 997 834 1,077

1 Heat treated-5 hrs. at 105C.

Table VPart III PHYSICAL PROPERTIES OF UNSATURATED BASE SHEETCREPED TAPE STOCKMEDI'UM BONDING Basis weigh NOTE.Base paper fiber furnish, unbleached spruce kraft, specifically Solka 15.

Table VI--Part I SATURANT FORMULATIONS-MAJOR COMPONENTS- AND SATURANT PICKUPSPARTS DRY SATURANT PER 100 PARTS DRY FIBER-ON MEDIUM HIGH BONDED FLATBACK TAPE STOCK Example M N 0 P Elastomer 2 100 100 100 100 Polar Adjunct 0 30 100 300 Antitoxidaut 1. 2 1. 2 1. 2 1. 2 Percent total solids 45 45 45 45 Pickup-pphp--- 77 73 73 1 See Table III-Part III for base paper physical properties and furnish.

Copolymer of styrene (26%) with butadiene (74%). Total solids- 60-62%. Emulsifier systemaniom'c. Particle sizelarge.

3 Acrylate copolymer of ethyl acrylate (85%), methyl methacrylate (10%), and carboxylic acid compound (5%).

Table VI-Part II PHYSICAL PROPERTIES OF SATURATED SHEETSHEAT TREATED (HT) AND UNTREATED (U)-FROM SATU- RANTS IN TABLE IV, PART I M N 0 P U HT 1 U HT 1 U HT 1 U HT 1 Basis weight 22.7 22.4 21.9 21.9 22.3 22.2 23.1 23.3 Apparent density- 5.11 5. 00 5.13 5.17 5. 14 5. 19 5. 44 5. 50 Tensile:

MD 3.2 3.4 3. 7 3. 9 4.8 4. 9 6.0 6.3 C 1.9 2.1 2.3 2.4 3.0 3.3 4.0 4.1 Stretch MD 12.0 6.1 26. 0 20. 5 15. 6 15. 5 6.5 6. 4 CD 14.3 13. 6 36. 0 30. 5 21.6 22. 0 12.4 11. 9 Wet tensile, MD 0.21 0.32 0.24 1. 04 0.43 2.07 0.61 2.82 Wet stretch, MD. 0.0 4.8 0.0 9. 5 3. 6 12.9 5.9 12.1 Delamination resist., MD 428 476 515 533 528 685 631 780 1 Heat treated 5 hours at 105 C.

Table VIIPart I SATURANT FORMULATIONS-MAJOR COMPONENTS AND SATURANT PICKUPSPARTS DRY SATURANT PER PARTS DRY FIBER-ON LOW BONDED FLAT STOCK Oentrifuged, ammonium hydroxide stabilized, Liberian natural rubber latex. Total solids60%.

1 Acrylate oopolymer of ethyl acrylate (85%), methyl methacrylate (10%), and a carboxylic acid compound (5%).

Table VIIPart II PHYSICAL PROPERTIES OF SATURATED SHEETS-HEAT TREATED (HT) AND UNTREATED (U)FRO1\1 SATURANTS IN TABLE VII, PART I Q R s '1 U V U H'I U HI U Hl U HT1 U HT! U HT! Basis Wei ht 37.0 35.5 37.7 36.3 35.3 36.0 ppail ent density 3.81 3. 38 3.59 3. 45 3.62 3.51

ens1 B1 1 Heat treated hours at 105 C.

Table VIIPart III 0 manner that the saturated sheet is split down the middle, PHYSICAL PROPERTIES OF UNSATURATED BASE andfinally Placmg "E two taPe ends leading to SPht SHEETLOW FIBER T0 FIBER BONDED UNAGED the aws of the tensile tester as a means of determining the P force required to sustain the splitting. In our case, strips ggig g i gg 2 g millimeters wideare tested, and the rate of splitting is Tensile sum /1b. 0109 at four inches per minute. Results are expressed in grams g? per 15 mm. strip width. 1m 0 01m Porgsit Frazier 17 Reflectance R3438 or brightness: The procedure for Tab 18 I determining the brightness is covered by TAPPI Standard SATUR 4N1 FORMULATIONS VIAJOR oo lPoyEyT Method T452;m 48 brightness of paper In the case of a i l l J. l. t. 1 AND SATURANT PIOKUP PARTS DRY SATURANT PER paper making fibers which inherently tend to be yellow in 100 PARTS DRY FIBER-ON LOW BONDED FLAT STOCK color, the brightness of a sheet is a measure of its poten tial whiteness. Most synthetic and natural polymers Example W X Y Z tend to also be yellow in color, thus the brightness of a combination of fibers and elastomers is a good measure $3 3? H g- 0 38-8 28 8 88-3 of the potential whiteness. ggg gg gj 145 The adjunct polymer may be employed in the range Percent totalllsolidsfl 281 281 23.0 23.3 from about 10 to about 200 parts, preferably about 20 Pwkulhpp p to about 80 parts, by Weight per 100 parts by weight of the elastomers. Within these ranges the properties of the 1 C0 01 er of acrylonitrile (31.57) with butadene (68.57). Total solids- 40 7? Emulsifier system-anionic rosin soap; particle size- 40 saturated Sheet are Optimum lhe Particular Saturant small600 composition emnloyed. 2A l t 00 01 i th 1 0 'late 85 moth '1 methacr late (10%?513 :arbgi1yl i c i1 id c01 np n nd (5%). S y Subsequent mechanical treatment of the saturated sheet gg gzg Table III for Unsaturated Sheet is often used to produce a variety of effects. Calender- Ta VIH Part H ing andtsgper falengerintg hTIIe befn useid Lo increasenthe apparen ensi y an 301 en e 33 urate s set as We as Y AL P PERTIES OF SATURATED SHEETS-HEAT E 2 3 AND UNTREATED (U) FROM to improve the surface for coating. For a number of end RANTS IN TABLE VIII uses it is desirable to emboss the saturated sheet With a variety of atterns and attern de ths.

p P p W X Y Z Saturated sheets described herein may be used for abrasive papers, glue coated tape stocks, pressure sensitive U U U HTI U tape stocks, protective masking sheets, artificial leather stocks, artificial chamois, pennant and banner stock, labels, fig g gfi gg 3 3 5 2 3 book cover stock, automobile trim panel base stock, pro- Tensile: jection screens, printing press top cover sheets, gaskets,

i2 5:2 2:8 3:3 2 1:; 1:2 2:? cloth replacements, window shades, and the like. Stretch 5 21 4 3 22 3 29 4 19 0 00 A distinct advantage of saturated sheets of the invention g 2&3 33%;; 2:; 4 13 the ability to meet the requirernent for high temperature Vet%nsil% 1 0.13 1. 42 0 2% 1. 51 0 2 2. 95 3. 5 end uses. Solvent resistance 18 also enhanced in the e s retc 0. a a; Fold, MD 130 430 165 331 260 735 400 1,310 egnated shwts dlsclosed it should be noted that nearly all of the ultimate 1 Heat treated 5 hows at 5 Q products require subrslequent coating, spreading, or laminat- 11'1 operations on t e saturated base sheet. Herein lies I 4 Y I g gg fii g fi 31:2; zg zgi g ifi g g gig xg; a distmctly advantageous feature of the disclosed saturated sheets. The "m to es 1- i I e defined m Common-On wlth Tables I and H except the s'iturant c In it ion t o fib rs 21122 21225: ii zsiii f following, which aresetforthbelow. 5 f .3, d U 1 e G d a 'M.I.T. r616: TAPPI Standard Method T423-m-50; 11, s? O if 2 1 i 1 e -1 Mlrrwfoldmg endurance. 3:071 e veen saturate s e ts o e inven ran an p as Wet tensile and stretch: These data are obtained in tlclzefi PY Y acrylates, the same manner as the dry properties with exception abrasive paper varn shes, animal glues, pressure sensltlve that the strips are completely wet with water and the masses, and llke 8 b ain d- I average loading rate is 0.6 kg./sec. Other modes of applying the principle of the 1nvent1on Delamination resistance: This test indicates the resistmay be employed, change being made a ga d the ance to internal splitting of a sheet. The test involves details described, provided the features stated in any ot adhering a cloth tape to each side of the sheet, mechanithe following claims or the equivalent of such be cally starting a separation of the cloth tape m such a employed.

We, therefore, particularly point out and distinctly claim as our invention:

1. A product comprising a sheet of cellulose fibers impregnated with a composition comprising an elastomeric polymer in admixture with a separate compatible adjunct polymer with specific adherence to said fibers, said elastomeric polymer selected from the class consisting of polymers and copolymers of conjugated dienes, and natural rubber, said adjunct polymer formed from about 0.5% to about 7% by Weight of at least one polymerizable :,fi-fithYl611lC carboxylic acid, at least 80% by weight of at least one alkyl acrylate in which the alkyl group has from one to four carbon atoms, and from 0 to 19.5% by weight of at least one alkyl methacrylate in which the alkyl group has from one to four carbon atoms, said adjunct polymer ranging from about parts to about 200 parts by weight per 100 parts by weight of said elastomer.

2. The product of claim 1 wherein said elastomeric polymer is natural rubber.

3. The product of claim 1 wherein said elastorneric polymer is a copolymer of acrylonitrile and butadiene.

4. The product of claim 1 wherein said elastomeric polymer is a copolymer of butadiene and styrene.

5. The process for preparing a product which com prises impregnating a sheet of cellulose fibers with a 14 liquid suspension of an elastomeric polymer in admixturewith a separate compatible adjunct polymer having specific adhesion to said fibers, said elastomeric polymer selected from the class consisting of polymers and copolymers of conjugated dienes, and natural rubber, said adjunct polymer formed from about 0.5% to about 7% by weight of at least one polymerizable a,/3-ethy1enic carboxylic acid, at least by weight of at least one alkyl acrylate in which the alkyl group has from one to four carbon atoms, and from 0 to 19.5% by weight of at least one alkyl methacrylate in which the alkyl group has from one to four carbon atoms, said adjunct polymer ranging from about 10 parts to about 200 parts by weight per parts by weight of said elastomer.

6. The process of claim 5 wherein the impregnated sheet is heat treated at a temperature of at least about 100 C. for a period of at least about 0.5 hour.

References Cited in the file of this patent UNITED STATES PATENTS 2,726,967 Eger Dec. 13, 1955 2,754,280 Brown et al. July 10, 1956 2,791,571 Wheelock May 7, 1957 2,843,561 Ingley July 15, 1958 2,848,105 Bartell et a1. Aug. 19, 1958 2,848,355 Bartell Aug. 19, 1958 

1. A PRODUCT COMPRISING A SHEET OF CELLULOSE FIBERS IMPREGNATED WITH A COMPOSITION COMPRISING AN ELASTOMERIC POLYMER IN ADMIXTURE WITH A SEPARATE COMPATIBLE ADJUNCT POLYMER WITH SPECIFIC ADHERENCE TO SAID FIBERS, SAID ELASTOMERIC POLYMER SELECTED FORM THE CLASS CONSISTING OF POLYMERS AND COPOLYMERS OF CONJUGATED DIENES, AND NATURAL RUBBER, SAID ADJUNCT POLYMER FORMED FROM ABOUT 0.5% TO ABOUT 7% BY WEIGHT OF AT LEAST ONE POLYMERIZABLE A,B-ETHYLENIC CARBOXYLIC ACID, AT LEAST 80% BY WEIGHT OF AT LEAST ON ELAKYL ACRYLATE IN WHICH THE ALKYL GROUP HAS FROM ONE TO FOUR CARBON ATOMS, AND FROM 0 TO 19.5% BY WEIGHT OF AT LEAST ONE ALKYL METHACRLATE IN WHICH THE ALKYL GROUP HAS FROM ONE TO FOUR CARBON ATOMS, SAID ADJUNCT POLYMER RANGING FROM ABOUT 10 PARTS TO ABOUT 200 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID ELASTOMER. 